Mercury control in a seawater flue gas desulfurization system

Abstract

A method for controlling mercury release, emission and/or re-emission levels in a treated flue gas and a seawater effluent waste stream through control of a sulphite concentration within a seawater scrubber system is disclosed. One method for controlling mercury release, emission and re-emission levels through control of sulphite concentration is to measure the sulphite concentration of seawater entering a seawater scrubber system and comparing the same to a predetermined sulphite concentration value. If the comparison reveals the measured sulphite concentration is above the predetermined sulphite concentration values, the amount of fresh seawater and/or oxidation air supplied to the seawater scrubber system is increased. If the comparison reveals the measured sulphite concentration is below the predetermined sulphite concentration values, the amount of fresh seawater and oxidation air supplied to the seawater scrubber system is decreased.

What is claimed is: 
     
       1. A method for controlling mercury release, emission and re-emission levels in a treated combustion flue gas and a seawater effluent waste stream comprising:
 supplying a combustion flue gas to a seawater scrubber system for direct contact with seawater for removal of contaminants from the flue gas to produce a treated flue gas and a seawater effluent waste stream; 
 measuring a sulphite concentration in the seawater entering a scrubber tower of the seawater scrubber system and in the produced effluent seawater for comparison to a predetermined sulphite concentration value; and 
 adjusting one or more seawater scrubber system parameters to increase or decrease sulphite concentration to control levels of mercury release, emission and re-emission in each the produced treated flue gas and the seawater effluent waste stream. 
 
     
     
       2. The method according to  claim 1 , wherein the sulphite concentration is measured in the produced effluent seawater. 
     
     
       3. The method according to  claim 1 , further comprising:
 measuring a mercury concentration in the seawater scrubber system for comparison to a predetermined mercury concentration value or a correlated predetermined sulphite concentration value; and 
 adjusting one or more seawater scrubber system parameters to increase or decrease sulphite concentration to control mercury release, emission and re-emission in the produced treated flue gas and seawater effluent waste stream based on the mercury concentration measured. 
 
     
     
       4. The method according to  claim 1 , further comprising:
 supplying an amount of an oxidation air to seawater effluent collected in the seawater scrubber system to adjust the sulphite concentration in the seawater dispersed by nozzles within the seawater scrubber system to control levels of mercury release, emission and/or re-emission in each the produced treated flue gas and the seawater effluent waste stream. 
 
     
     
       5. The method according to  claim 1 , wherein the sulphite concentration is measured using one or more sulphite sensors. 
     
     
       6. The method according to  claim 1 , wherein adjusting one or more seawater scrubber system parameters comprises adjusting fresh seawater supply, adjusting oxidation air supply, or adjusting both fresh seawater and oxidation air supply, to the seawater scrubber system. 
     
     
       7. A system for controlling mercury release, emission and re-emission levels in both a treated combustion flue gas and a seawater effluent waste stream comprising:
 a seawater scrubber system with seawater dispersal for direct contact with a combustion flue gas flowing therethrough; a collection tank for collecting effluent seawater produced by direct contact with the combustion flue gas; 
 one or more sulphite sensors arranged in contact with seawater entering a scrubber tower of the seawater scrubber system for dispersal therein and in the produced effluent seawater, for measuring a sulphite concentration in the seawater to obtain a measured sulphite concentration; 
 a control device to compare the measured sulphite concentration to a predetermined sulphite concentration value and based thereon control a device; and 
 a device controlled by the control device for adjusting a seawater scrubber system parameter to increase or decrease sulphite concentration to control levels of mercury release, emission and/or re-emission in each the produced treated flue gas and the seawater effluent waste stream. 
 
     
     
       8. The system of  claim 7 , further comprising: one or more mercury sensors in an outlet of the seawater scrubber system for measuring a mercury concentration to obtain a measured mercury concentration. 
     
     
       9. The system of  claim 7 , further comprising:
 one or more mercury sensors in an outlet of the seawater scrubber system for measuring a mercury concentration to obtain a measured mercury concentration; a control device to compare the measured mercury concentration to a predetermined mercury concentration value or a correlated predetermined sulphite concentration value and based thereon control a device; and 
 a device controlled by the control device for adjusting a seawater scrubber system parameter to increase or decrease sulphite concentration in the seawater to control levels of mercury release, emission and re-emission in both a produced treated flue gas and seawater effluent waste stream. 
 
     
     
       10. The system according to  claim 7 , wherein the seawater scrubber system parameter adjusted is an amount of oxidation air supplied to effluent seawater collected in the seawater scrubber system. 
     
     
       11. The system according to  claim 7 , further comprising: a valve controlled by the control device for adjusting an amount of fresh seawater supplied for nozzle dispersal within the seawater scrubber system. 
     
     
       12. The system according to  claim 7 , further comprising: a blower controlled by the control device for transporting an amount of oxidation air to the effluent seawater collected in the seawater scrubber system. 
     
     
       13. The system according to  claim 7 , further comprising:
 a valve for adjusting an amount of fresh seawater supplied to the seawater scrubber system and a blower adjustable to vary an amount of oxidation air supplied to effluent seawater collected in the seawater scrubber system to adjust the sulphite concentrations therein to control levels of mercury release, emission and/or re-emission in each the produced treated flue gas and the seawater effluent waste stream. 
 
     
     
       14. The system according to  claim 7 , wherein the control device includes a memory device.